3GPP (3rd Generation Partnership Project) has defined only a function of monitoring failures at an application layer. However, there is a problem with this function that failures in a device itself cannot be detected. Moreover, another problem is caused regarding the continuity of communication services for users, because it takes a long time for the monitoring at the application layer to detect failures.
PTL 1, for example, discloses a technique for addressing these problems. A network monitoring device disclosed in PTL 1 is connected to a plurality of radio base stations through an RNC (Radio Network Controller) or a GW (Gateway), and monitors failures occurring in the respective radio base stations. This network monitoring device detect a failure occurring in a certain radio base station, and then causes a neighboring radio base station to complement coverage (range within which radio communication can be conducted) of the radio base station in the failure state.